The first two terms are meant to constrain the capacity of representation \(z^i\) , and the last two reinforce the reconstruction. VAEs model use (REF ) and () to achieve, and adversarial autoencoder [1]} use the KL divergence () between the posterior distribution \(q_{\phi }(z^i)\)  and prior \(p(z)\)  to constrain the capacity of representation and get better representation.
